“Summary of Unit 2”
Essential things to know for the end-of-the-Trimester test on Living Environment
Organization of living things:
[smallest] Cells → Tissues → Organs →
Organ Systems → Organism [largest]
Organelles are the small parts that make up a cell (each has at least one specific function)
a. Vacuoles – store waste and water (large in plant cells, small in animal cells)
b. Ribosome – (very small and is often represented by a dot) located on the “Rough
ER” or in cytoplasm. Ribosomes are where proteins are assembled (protein synthesis
from amino acids).
c. Mitochondria – (The Powerhouse of the cell where energy is extracted from “food”)
the Site of cellular respiration in both plant and animal cells.
Formula for cellular respiration:
Glucose + Oxygen
Carbon Dioxide + Water + ENERGY (ATP)
d. Chloroplasts – only in plant cells; where the process of photosynthesis occurs.
Formula for photosynthesis:
Sun’s energy + Carbon Dioxide + Water
Glucose + Water + Oxygen
e. Nucleus – the control center of the cell and contains DNA (the program or code of life)
f. Cytoplasm – the liquid (gel) media that fills the cell.
g. Cell Membrane –
1. separates the contents of the cell from the outside environment
2. controls the transport of materials into and out of the cell. (selective permeability)
Homeostasis is the ability of an organism to maintain a stable internal balanced environment.
Metabolism is the sum of all the chemical reactions that occur within the cells of an organism.
The most common elements that make up living things are carbon (C), hydrogen (H), oxygen (O), and
nitrogen (N). Atoms combine together (bond) to form a chemical bond. When chemical bonds are
formed, energy is stored (energy is released when the bond is broken).
Organic molecules contain Carbon (C) and Hydrogen (H).
Carbohydrates: contain C, H, and O (Oxygen), with ratio of hydrogen to oxygen 2:1
Lipids (Fats): another kind of CHO compound. Lipids have many more bonds than sugars and can
therefore store much more energy.
Organic Molecule
Carbohydrates (starch)
Proteins (contain Nitrogen)
Lipids
Basic Unit - (Lego Blocks)
Glucose (Simple Sugars)
Amino Acids (20 essential kinds)
Fatty Acid & Glycerin
Foods found
Grains, vegetables, fruit
Meat, egg whites, beans
Animal fats, nuts, oils
Diffusion is the movement of molecules from areas of high concentration to areas of low
concentration. (in the direction of the Concentration Gradient)
Osmosis is the diffusion of water through a membrane.
Facilitated Diffusion: example - special channel proteins that aid glucose molecules to enter thru
the cell membrane
Passive Transport (Diffusion, Osmosis and Facilitated Diffusion belong to this category)
No energy needed – this is similar to water flowing downhill). These processes try to equalize the
concentrations of a substance.
Active Transport is the moving a molecule from LOW concentration to a HIGH concentration
(Uses energy in the form of ATP – Active Transport is comparable to water being pumped uphill).
Example of active transport: Sodium-Potassium Pump in animal cell membranes – Pumps
Sodium out of the cell, and pumps Potassium into the cell, both from respective LOW to HIGH
concentrations.
Solute vs Solvent: A solvent is a liquid that dissolves a solid, liquid or gaseous solute. A solute is a
substance dissolved in another substance. A solute and a solvent make up a solution. The solute is
usually present in a smaller amount than the solvent.
An example of this would be dissolving a teaspoon of table salt in water. Water is the solvent and the
salt is the solute and together they make a salt (saline) solution.
An example: The membrane is permeable to salt and water, but not to sugar.
Picture shows the start.
Water concentrations are:
Left: 90% ( = 100% – 5% (sugar) – 5% (salt) )
Right: 80% ( = 100% – 20% (salt) )
So, water will move thru the membrane to the Right – level rises
Salt % higher on the Right, so some Salt moves to the Left
Hypertonic, Isotonic, Hypotonic Solutions
“Tonicity” is defined in terms of solute concentration
Hypertonic solution: Latin Hyper means above or over, in the solute, so the water concentration
is lower here. So, if you placed a cell in a hypertonic solution, water will flow out of the cell, s0 cell
shrinks.
Hypotonic: opposite / Isotonic: equal “tonicity” inside and outside
Example:
Cell (oval) placed in a hypotonic solution. Hypotonic because the solution has
a lower solute concentration (30%) than the cell (40%).
Picture shows the start.
Water concentrations are:
Inside the cell: 60% (the difference between 100% and 40% - the solute)
Outside the cell: 70% the difference between 100% and 30% - the solute)
So, the Water concentration is higher outside the cell.
Water will move thru’ the membrane in to the cell, causing it to swell, and
possibly burst (if it is an animal cell which doesn’t have cell wall like a plant
cell.)
Human Body Systems:
Name of
system
What it does
Parts of the system
* Organelles with the
same function
Digestive
breaks down food into
nutrients & puts them
in the blood stream
mouth, esophagus,
stomach, small
intestine, large intestine,
rectum
+ enzymes from liver, gall
bladder, pancreas
Vacuole and Lysosome
Circulatory
carries gasses and
nutrients throughout
the body
heart, arteries, veins,
capillaries
Cytoplasm, ER and the
Golgi Apparatus
Respiratory
exchanges carbon
dioxide and oxygen
lungs, bronchi, alveoli,
diaphragm
Cell Membrane
Urinary /
Excretory
removes wastes from
the blood and then
from the body
kidneys, bladder,
urethra
Cell Membrane or vacuole
brain, spinal cord, nerve
cells
Nucleus
Pituitary, Thyroid,
Adrenal, Pancreas,
Gonads
Nucleus
Nervous
Endocrine
Fast control of the
functioning of
body systems thru’
neuron connections
Slow control of the
functioning of
body systems thru
hormones carried via
blood
* In a single-celled organism, the functions of the Organ Systems are performed by organelles
Control - Chemicals produced in the endocrine glands (HORMONES) and chemicals produced by
nerve cells are primarily responsible for communication between cells.
Hormones are secreted by the endocrine glands located at various parts of the body. They travel thru
the bloodstream until they find matching RECEPTOR SITES.
Dynamic Equilibrium is a steady state-balance - : HOMEOSTASIS
Negative Feedback - controls hormone levels to maintain homeostasis.
Analogy = Thermostat; as the temperature in your house goes up, the thermostat
turns your heat off; as the temperature goes down, the thermostat turns on. This
maintains a balance or a comfortable home.
A good example is how our body regulates the amount of sugar in our blood:
When glucose (sugar) levels are above normal the pancreas secretes INSULIN. This
hormone prompts glucose to move from the blood into body cells, resulting in a lower glucose level
in the blood. Another hormone secreted by the pancreas (glucagon) works in the opposite way. When
the glucose level in the blood is too low, this hormone prompts the release of glucose stored in the
liver which raises BLOOD SUGAR LEVEL.
Cellular Respiration is the process used by ALL organisms to produce energy by
using oxygen to burn sugar in order to release energy in the form of (ATP). Organelle used in this
process: Mitochondria
Digestion- breaking large molecules down into smaller molecules.
1. Proteins are broken down into Amino Acids.
2. Carbohydrates and Starches are broken down into Simple Sugars (Glucose).
3. Fats (Lipids) are broken down to Fatty Acids & Glycerol
Transport - involves the movement of materials inside the cell as well as the movement between
parts of a multicellular organism.
Excretion - the removal of all waste produced by the cells of the body.
Synthesis is the making or building of large molecules from smaller ones.
Photosynthesis is the process of storing the energy from the sun in the chemical bonds of
glucose (sugar) Organelle used in this process: Chloroplast
Formula for Photosynthesis:
Enzymes*
Sunlight (energy) + Carbon Dioxide + Water ----------à Glucose + Oxygen
Where is photosynthesis carried out? Chloroplasts of Producers (plants)
Cellular Respiration occurs in the Mitochondria of All Organisms both plants and animals
Enzymes*
Glucose + Oxygen ----------à
Carbon Dioxide + Water + Energy (ATP)
* In chemical equations, enzymes (catalysts, in general) that are necessary to facilitate or
accelerate the reaction are listed above the arrow.
A catalyst is a chemical that increases the rate of a chemical reaction without itself being
changed by the reaction.
Enzymes – serve as biological catalysts needed for chemical reactions, especially in digestion and
synthesis. Digestive enzymes help your body digest food, for instance. They split complex molecules
into simple forms (catabolism) for your body to use. – see picture below. Some other enzymes help
to synthesize (join) molecules (anabolism).
Enzyme reaction rates are affected by:
1. Shape - “Lock and Key Model” if the shape changes (due to heat) it will not work.
2. Temperature - each enzyme works best at a specific temperature (body temp 37 C)
3. pH- each enzyme works best at a specific pH
pH value (a number in the pH scale 0-14) is a measure of how acidic or alkaline a liquid is.
Food chains & Food Webs:
Producers, or autotrophs, make their own organic molecules. Consumers, or heterotrophs,
get organic molecules by eating other organisms.
A food chain is a linear sequence of organisms through which nutrients and energy pass as one
organism eats another. In a food chain, each organism occupies a different trophic level, defined by
how many energy transfers separate it from the basic input of the chain.
Food webs consist of many interconnected food chains and are more realistic representation of
consumption relationships in ecosystems.
Energy transfer between trophic levels is inefficient—with a typical efficiency around 10%.
This explains the Energy Pyramid of trophic levels which narrows as it goes higher. This
inefficiency limits the length of food chains.
The energy transfer between trophic levels is inefficient because energy is lost when one
trophic level goes to a level higher. This is due to the fact that an organism is not fully consumed.
Transportation of the actual organism within the consumer requires energy. Also heat is lost in the
conversion from the organism to energy to the consumer. Finally, waste is often a by-product and
this is energy that is lost and could not be converted.
Primary consumers are usually herbivores, plant-eaters, though they may be algae eaters or
bacteria eaters. Upper level consumers are generally meat-eaters—carnivores. Omnivores that
can eat both plants and animals.
Decomposers (such as Fungi, bacteria, and worms) play a critical role in keeping ecosystems
healthy. When they break down dead material and wastes, they release nutrients that can be recycled
and used as building blocks by primary producers.
Regarding Experiments:
Independent Variable (IV) is the one thing that “I change” to test my hypothesis.
Dependent Variable (DV) is the thing that changes because of the IV (DATA collected)
Example: Experiment to investigate The Effect of Sunlight (IV) on plant growth (DV).
Control Group is the group that is studied under the normal conditions (that is without changing
the independent variable).
Experimental Group is the group that is identical to the control group with the ONE
CHANGE or difference (the Independent Variable).
Organizing Data
Where does the Independent Variable (IV) go on a data table? What about the Dependent
Variable (DV)?
Independent Variable
Dependant Variable
Graph on the X - axis
Graph on the Y axis
Example: sunlight
Example: growth
Where does the Independent variable go on a graph? - X axis (horizontal)
What about the Dependent variable?
Labeling a graph:
1. Title the graph (The effect of _____ on _______.)
2. Label the X and Y axis.
3. Determine a proper scale for X and Y axis.
4. Set up a key or legend if necessary.
How can you make an experiment more valid?
Repeat the experiment / Increase the number of specimens or trials / Peer review
Parts of the microscope:
1. Eyepiece: the part that you look through (closest to the eye) usually 10x
2. Objective Lens: the magnifying part closest to the slide (high power=usually 40x; low
power=usually 10x)
3. Fine Adjustment Knob: used to focus on low & high power
4. Course Adjustment Knob: used to focus only on low power
5. Stage: where the slide is placed
6. Stage Clips: hold the slide in place
7. Diaphragm: controls the amount of light used
How to calculate total magnification: if a microscope has a 10X eyepiece, and 10X and
40X objectives.
Total Magnification on low power: 10 X 10 = 100X (it looks 100 times bigger than real life)
Total magnification on high power: 10 X 40 = 400X (it looks 400 times bigger than real life)
If you looked at the
e
letter under a microscope, what would it look like?
1. Mirror image and flipped up side down.
2. Increasing magnification reduces the field. (Larger image but you see less of it)
3. Increasing the magnification reduces the amount of light. (Field darkens)